Most of the treatment literature for young children with autism consists of either full-scale, comprehensive intervention programs evaluated on broad outcomes, or highly specialized interventions evaluated on narrowly focused outcomes. Neither approach has succeeded in describing for whom, and under what conditions, a given intervention should be used. The present project will describe a sequential approach for identifying and testing potential predictors of responsiveness to interventions for specific skill deficits. Motor imitation is the core skill addressed in this project, because it not only plays a pivotal role in the social and cognitive development of children with typical development, but also has been described as a core deficit for young children with autism. Three studies will be conducted with 2- and 3-year-old children with autism. Study 1 will identify which organismic factors (i.e., developmental precursors of the target skill) and environmental factors (e.g., family risks and opportunities) are predictors of motor imitation development, using a longitudinal correlational design. Study 2 will evaluate the effectiveness of a novel imitation intervention that combines both contingent imitation and embedded trials, on children who are high on the predictors identified in Study 1. Study 3 will determine whether the intervention is differentially effective in increasing generalized imitation in children who score high and low on the predictor skills. The results of this research will have implications for the design of interventions for other core deficits of autism.